1. Field of the Invention
The present invention relates to the treatment and maintenance of molds used in manufacturing glass parts and more particularly relates to the application of a composition comprising monoaluminum dihydrogen phosphate, Al(H.sub.2 PO.sub.4).sub.3, as a binder and an anti-wear agent such as solid lubricant, finely divided hard metal, or the like to the surfaces of such a mold to enhance the quick release of a molded glass part therefrom and to protect the mold.
2. Description of the Prior Art
In accordance with the conventional techniques employed in molding glass parts such as bottles, jars, and the like, the mold surface is frequently treated with a release by a process known as swabbing. In accordance with swabbing techniques, a swabbing composition, comprising a mineral oil carrier and a lubricant such as sulphur and/or graphite, is brushed into the glass forming equipment about every five to forty-five minutes. The swabbing compound is brushed into the mold to allow the molded glass part to be released from the mold without any marks on it and also to preserve the mold against deterioration during the molding process.
Numerous disadvantages have been encountered in using such swabbing techniques. First, in accordance with the conventional swabbing method, the mold must be polished before the swabbing compound is applied. Since such a polishing operation by its very nature involves the removal of metal from the mold, the useful life of the mold is necessarily reduced as the metal is gradually worn away.
In addition, because of the chemical composition of swabbing compounds, chemical reactions occur between the swabbing compounds, the base metal of the mold, and hot glass. Thus, when subjected to heat and exposed to oil, hot glass, sulphur and graphite, corrosive materials such as sulfuric and nitric acids are formed, and these acids attack the exposed metals of the mold and other equipment.
Furthermore, because of the manual brushing techniques employed in applying swabbing compounds to glass molds, an uneven coating of the swabbing compound is applied. As a result, during the molding operation temperature gradients are set up due to the uneven thickness of the swabbing compound, thereby resulting in the production of defective glass parts. The build-up of swabbing compounds in the molding equipment further results in the production of out of specification glass parts because of improper mold dimensions. The use of oily swabbing compounds frequently results in molded parts of unsightly, discolored glass which must also be rejected.
Finally, the use of oily swabbing compounds results in the production of significant amounts of smoke due to the heat at which the glass molds are operated. As a result, conventional oil swabbing techniques pose significant compliance problems under air pollution control regulations.
In accordance with the present invention, a new technique for treating molds employed in manufacturing glass parts permits the molded glass part to be quickly released and provides virtually complete protection for the mold surface while avoiding the foregoing disadvantages prior art swabbing technique.
Accordingly, it is a primary object of the present invention to provide a new method for treating glass manufacturing molds.
A related object is to provide compositions for use in accordance with such process.
A further object is to provide a method for treating molds used in manufacturing glass parts which avoids the disadvantages of the prior art swabbing techniques.